1. Field of the Invention
The present invention generally relates to an apparatus for gas treatment, and more particularly to a gas treatment apparatus with surrounding spray curtains.
2. Description of Related Art
In semiconductor manufacturing processes such as thin film deposition processes or chemical vapor deposition (CVD) processes are carried out inside a chamber provided with a showerhead, wherein semiconductor wafers are placed on a wafer carrier with a heating function and the showerhead sprays reaction gases required for the processes into the chamber and over the semiconductor wafers on the wafer carrier. When reaction gases such as precursor gases containing materials to be deposited are sprayed onto the semiconductor wafers through the showerhead in a gas state, a chemical reaction occurs within the chamber, and thus the thin film is formed. During the chemical reaction, a high temperature must be maintained inside the chamber for the chemical reaction.
The showerhead usually has a gas distribution injector for directing the precursor gases towards the wafer carrier in the chamber where the semiconductor wafers can be treated for processes. Ideally, the precursor gases are directed at the wafer carrier such that the precursor gases react as close to the wafer and distribute as uniform as possible over the semiconductor wafers.
In many metal organic chemical vapor deposition (MOCVD) processes, for example, combinations of precursor gases comprised of metal organics and hydrides, such as ammonia or arsine, are introduced into a chamber through the showerhead. Process-facilitating carrier gases, such as inert gases, argon or helium, also may be introduced into the chamber through the showerhead. The precursor gases mix in the chamber and react to form a thin film on a semiconductor wafer held within the chamber. The carrier gases typically aid in maintaining laminar flow at the wafer carrier.
However, many existing showerheads have problems that may interfere with efficient operation or uniform deposition due to the design of gas channel. For example, gas spray in existing showerhead may induce significant space in the chamber without effective gas flow from the gas vents of the showerhead to the semiconductor wafer resulting in a non-uniform distribution of gases.
The non-uniform distribution of gases may cause unwanted deposition or non-uniform deposition. Such unwanted deposition consumes reactants and decreases the efficiency and the non-uniform deposition would further reduce the throughput of the process. Thus, many current systems require frequent cleaning of the reactor, which further reduces productivity.
Since a high temperature must be maintained inside the chamber for the chemical reaction, uniform and efficient cooling channel design is crucial for maintaining the efficiency, throughput and productivity of the reactor. Some existing showerheads also have problems of efficient operation or uniform deposition due to the cooling design. Owing to the inefficient cooling design, the formation of condensates on the showerhead as well as gas phase particle formation and the production of undesirable precursor reactant products may adversely affect the composition of the thin film deposited on the semiconductor wafers. In U.S. Patent Application No. 20070163440, the gas separation type showerhead which separately provides two different gases without cooling design might cause reaction and undesirable deposition on the holes and vents and form obstacles to the gas flows. In U.S. Pat. No. 7,976,631, each the heat exchanging channel of the showerhead is arranged only adjacent to one side of two adjacent gas channels and such cooling design obviously cannot provide uniform heat exchange. In U.S. Patent Application No. 20090095222, the gas mixing channel and the heat exchanging channel of the showerhead both are spiral channels wherein the gas mixing channel is disposed adjacent to the heat exchanging channel. The heat exchanging channel is also arranged only adjacent to one side of two adjacent gas channels and this inefficient cooling design would result in the formation of condensates on the showerhead as well as gas phase particle formation.
Therefore, there is a need for an improved deposition apparatus and process that can provide uniform thin film deposition and heat exchanging performance.